Enhanced Local Area (eLA) solution aims to design a local area system providing high performance on peak data rate, cell capacity, quality of service (QoS) guarantee, interference management, etc. Low cost and high energy efficiency are also expected for the eLA system. A base station (BS) is located in a radio access network (RAN) side which provides the local area network, just like home enhanced node-B (HeNB) in the LTE system, which is sometimes referred to as low power node (LPN) or eLA AP (access point) hereafter. User equipment (UE) maintains two connections with macro-eNB and LPN, which are called “dual radio connections”. A macro network connection is more stable and more carefully managed so that UE does not easily lose its connection, while a eLA connection is there more like for providing high speed data service in the local area.
The eLA system is expected to provide high performance service for users, with low cost, and is expected to become a competitor to Wi-Fi.
In current eLA architecture and protocol concept, it is a challenge of effective and efficient handover from source eNB towards a LPN (such as an eLA access point (AP)) which is not associated with the source eNB, e.g., the eLA AP has no simplified or modified S1 interface with the source eNB. Such handover may for example comprise handover from a source macro eNB to an eLA AP which is associated and thus controlled by another macro eNB and is not associated with the source macro eNB. For another example, in the case that a user equipment (UE) is served by a source eLA AP controlled by a first macro eNB and is going to handover to a target eLA AP controlled by a second macro eNB, wherein there is no association between the two eLA APs, effective and efficient processes of the handover are also expected.
According to existing schemes, to enable a UE handover from a macro eNB to an unassociated target eLA AP, a straight forward approach is to conduct an X2-based handover from source macro eNB to a macro eNB which controls the target eLA AP, and then conduct a separated macro eNB to eLA AP offloading. In other words, the UE is not handed over directly to the target eLA AP.
Since the existing scheme changes radio connectivity modes (single to dual connectivity radio or dual to single connectivity radio) via separated on-loading and offloading procedures, undesired signaling overhead, service interruption, QoS degradation, and the like are introduced.
In view of the foregoing problem, there is a need to design a solution for handover the UE between unassociated nodes in a heterogeneous network, so as to improve service continuity, reduce signaling overhead, increase signal quality and improve load balance in the heterogeneous network.